Search for Puneet Nehra, 43, a resident of Sugarland suburb and originally from Noida, Uttar Pradesh, continues in the Brazos river by authorities using boat and helicopter.
On his way home from picking up dinner for his family, Nehra and another driver stopped to help people involved in a crash on the Brazos River bridge of the northbound Grand Parkway on Sunday, Fort Bend County Sheriff's Office Spokesman Maj Chad Norvell.
Before deputies could respond to that first accident, another car operated by a suspected drunken driver crashed into the scene about 9 pm.
Police suspect that Nehra was knocked over the railing by the second car into the river.
Mr Norvell has asked public to call with any information about the crash or if they have seen the missing man, Nehra.
"Nobody saw him get knocked into the water. They didn't realise that was what happened until they had more vehicles than they had drivers," Mr Norvell said.
"They went to his residence nearby to make sure he didn't just walk home," Mr Norvell said.
His family told deputies he had not yet returned home. Mr Norvell said that's when officers pieced it together that Nehra likely was knocked off the bridge and into the river.
Gregory Kure, 30, has been arrested and charged with DWI in the incident, although Mr Norvell said those charges might change if Nehra is not found alive.
According to Consulate General Houston, P Harish, the search is going on.
Police was still undertaking the search and there was no further news. Rains are making it hard to continue the rescue operations.
Texas EquuSearch, a rescue organisation dedicated to searching for missing persons, are working to find him.
"So much debris underneath the water when we're doing sonar work and then actually where he went in at, it goes out into like 48 feet deep so we got some pretty deep water," said Tim Miller of Texas EquuSearch.
But recovery teams aren't giving up hope. "We made a commitment to stay here so we are going to stay until we feel as though there's nothing else we can do," said Mr Miller.
Follow NDTV for latest election news and live coverage of assembly elections 2019 in Maharashtra and Haryana.
Subscribe to our YouTube channel, like us on Facebook or follow us on Twitter and Instagram for latest news and live news updates.