The Latest from the IAAF world championships (all times local):

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12:40 p.m.

The Jamaican teams advanced fastest in both men‘s and women’s 4x100-meter relay heats at the world championships on Saturday.

Usain Bolt, who won the 100-200 sprint double, didn‘t run in the Jamaican team that won the second heat in 37.41 seconds. France surged into second place with a strong anchor leg from Jimmy Vicaut to finish in 37.88, narrowly ahead of China, which qualified in an Asian record 37.92.

The American men won their heat in 37.91, with Justin Gatlin running the second leg and exchanging the baton with Tyson Gay. Britain was second in 38.20.

Shelly-Ann Fraser-Pryce anchored the Jamaican women’s team to victory in the first heat in 41.84 seconds, the world-leading time this season.

Allyson Felix ran a strong second leg to help the Americans win the next heat in 42.00, the second-fastest qualifying time.

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11:50 a.m.

Sanya Richards-Ross finally got her turn on the track at world championships.

“Bitter, bittersweet,” the American called it.

The 2012 Olympic champion at 400 meters failed to qualify for her signature event and came to China this year as part of the 4x400 relay team. She has been hanging at the team hotel for two weeks, waiting to race.

She ran the third leg Saturday and increased the lead to help the Americans easily advance to Sunday‘s final.

A win there, and she could leave the Bird’s Nest with a gold medal to write a nice closing chapter to a difficult stay in Beijing.

She says she‘s having a good time, and enjoying mentoring the younger runners on the team. But she wants to do more running next year at the Olympics in Rio de Janeiro.

“I’m going to train so hard,” she said. “I don‘t want to feel like this again.”

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11:35 a.m.

Defending champion Ashton Eaton stayed within world-record range after seven events in the decathlon, amassing 6,451 points after the discus throw.

Eaton, who set the world record at 9,039 points in 2012, threw 44.34 meters and had a 131-point lead of Damian Warner of Canada. Warner cut Eaton’s overnight lead by 42 points with better marks in the 110-meter hurdles and the discus throw on Saturday.

Rico Freimuth of Germany was in third place with 6,266 points, recording the best mark of 50.17 meters in Group A of the discus throw.

The pole vault, javelin throw and 1,500-meter race are still to come in the decathlon.

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11:15 a.m.

Matej Toth of Slovakia won the longest event at the world championships, capturing gold in the 50-kilometer walk in 3 hours, 40 minutes, 32 seconds.

Toth, the 2014 European silver medalist, broke away from the other walkers shortly after the start and raced nearly the entire course on his own, stopping only briefly for a bathroom break.

He came into this year‘s world championships in top form, setting the third-fastest time in history in his native Slovakia in March.

It’s the first gold ever for Slovakia at the world championships.

Jared Tallent of Australia, a two-time Olympic silver medalist, finished more than a minute behind Toth in second. Takayuki Tanii of Japan took bronze. Defending champion Robert Heffernan of Ireland was fifth.

Veteran walker Jesus Angel Garcia of Spain, competing in his 12th world championships at the age of 45, finished in ninth place. He won gold more than two decades ago at the 1993 worlds in Stuttgart.

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11 a.m.

The U.S. teams qualified fastest for the men‘s and women’s 4x400-meter relay finals at the world championships.

The American women led at every split and finished in 3 minutes, 23.05 seconds to beat Britain (3:23.90) and France (3:24.86) in their heat on Saturday. Nigeria had the second-fastest qualifying time, winning the first of the women‘s heats in 3:23.27.

In the second of the men’s heats, Jamaica led at the first two changeovers before the Americans rallied to win in 2:58.13. Trinidad was second in 2:58.67, edging Jamaica by 0.02.

Britain won the earlier men‘s heat in 2:59.05.

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9:55 a.m.

Matej Toth of Slovakia leads the 50-kilometer walk just past the halfway point, widening his lead over his nearest competitors to 55 seconds.

Toth, who has the third-fastest time in history, passed the 30-kilometer mark in 2 hours, 13 minutes, 14 seconds.

Defending champion Robert Heffernan of Ireland and two-time Olympic silver medalist Jared Tallent of Australia were in a group of walkers behind Toth, alongside Zhang Lin of China and Japanese teammates Takayuki Tanii and Hirooki Arai.

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9:30 a.m.

Ashton Eaton leads the decathlon by 165 points after six events, placing second to Damian Warner of Canada in the 110-meter hurdles on Saturday.

Warner won the last of the decathlon sprint hurdles heats in 13.63 seconds, reducing the margin by eight points to Eaton, who recorded 13.69.

Eaton, the Olympic and world champion, had 5,718 points with the discus throw, pole vault, javelin and 1,500 meters to go.

Warner was in second with 5,553 points and Rico Freimuth of Germany was third with 5,392.

Yordani Garcia of Cuba crashed in the last heat of the hurdles, slipping to 25th place. Two-time world champion Trey Hardee withdrew on Friday after injuring his back in the long jump.

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8:45 a.m.

Matej Toth was leading the 50-kilometer walk after 15K in the world championships.

Toth, who has the third-fastest time in history, passed the mark in 1 hour, 7 minutes, 28 seconds and was 39 seconds clear of Jared Tallent of Australia, a two-time Olympic silver medalist.

Defending champion Robert Heffernan of Ireland, Mario Jose Dos Santos of Brazil and Lukasz Nowak of Poland were part of a group a further 10 seconds off the pace.

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7:40 a.m.

The 50-kilometer walk got under way Saturday morning, minus the only Russian entered in the competition.

Alexander Yargunkin was entered in the race but did not start amid reports that he did not travel to China because of the recent doping scandal engulfing race walking in Russia.

Jared Tallent, the two-time Olympic and two-time world championship silver medalist from Australia, was among the early leaders. (AP)