Fifty-two workers were trapped early Sunday when a torrent of mud and water engulfed a rail tunnel under construction in central China.

Rescue teams managed to free 35 of the workers building the tunnel in Hubei province and the remaining 17 trapped about 200 metres (660 feet) below ground would soon be freed, the Xinhua New Agency added.

Earlier reports said 38 workers were trapped in the accident

Heavy rains have triggered severe flooding and mudslides across many areas of central China in recent weeks.

According to Xinhua news agency, 78 people died and 18 are still missing after three days of downpours set off flash floods in Henan province in the past week.

More than 700 people have been killed by floods, landslides and lightning this year in China, according to latest official figures that have yet to tally the past week's casualties.