The collision between the private luxury bus and the tanker took place around 7 am, police said.
Resident Deputy Collector Manoj Gohad said rescue operations have already been launched.
"The disaster management machinery has been pressed into service and medical teams have been dispatched to the accident site," he said.
The injured were rushed to various hospitals around Dahanu, Additional Collector Ashok Shingare said, adding the critically injured were being shifted to hospitals in Mumbai.
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