NAIROBI, March 16 (Xinhua) -- Kenyan authorities said Friday that a section of the busy Nairobi-Mombasa highway has been reopened after Athi River bridge collapsed, causing traffic disruptions.

The Kenya National Highways Authority (KeNHA) said the water level at Stoney Athi Bridge has reduced to safe levels and repairs to erosion-damaged approaches are in progress.

"While the bridge has now been re-opened to traffic, road users are requested to exercise care and strictly follow traffic control instructions from the officers on site," KeNHA head of communication Charles Njogu said in a statement.

Several motorists were stranded for the better part of Thursday night after the Stoney Athi Bridge went down due to heavy rain.

Torrential rain, which is pounding many parts of Kenya, has resulted in floodwater overtopping bridges, cutting off highways, disrupting business and displacing people.

Chinese contractors moved swiftly on Thursday to repair the bridge at the busy road, which connects the capital city of Nairobi and the port city of Mombasa.

Sun Yingtuan, an official at the China Railway 21st Bureau, which is constructing the second carriageway of Mombasa road, said engineers were immediately mobilized following the collapse of the bridge to allow the transport to resume on Friday morning.

"Since 7:10 p.m. (Thursday), all staff, equipment and material have been contributed to fight the flood emergencies under instructions of the employer KeNHA and resident engineer," he said.

Sun said the contractors filled the bottom with huge stones that allows water to flow through stone gaps and then recover the pavement with filling materials.

Meanwhile, KeNHA said the main bridge at the Kangundo-Kamulu road, which also collapsed on Thursday, has been repaired.

"The bridge is therefore closed to traffic for safety reasons until water levels recede. The situation is being monitored constantly and the public will be advised promptly of developments," said KeNHA.

Following heavy rain on Thursday, four people were reported dead in Kitui when the charcoal-laden lorry they were travelling in was swept away by raging water while two others died in Kajiado County.

Kenya Meteorological Service on Thursday warned that heavy rains will continue in many parts of the country for the next few days.