Thirty-three villages on the banks of the Tansa river in Thane and Palghar districts were on Tuesday put on alert following heavy rains, an official said.
Santosh Kadam, chief of Thane's Regional Disaster Management Cell, said a dam in the vicinity was in danger of overflowing, which in turn could cause the river to flood.
"A total of 18 villages from Thane and 15 in Palghar have been put on alert. These areas are in Sahapur, Bhiwandi, Wada and Vasai talukas. The present level of the Tansa Dam is 125.55 MTHD while the overflow mark is 128.63 MTHD. We have been told by the Brihanmumbai Municipal Corporation, which owns the dam, to intimate villagers," he said.