KOLKATA, India (AP) — An Indian port official say two Chinese sailors were found dead from inhaling coal fumes in the cargo hold of their Chinese bulk carrier.

A senior official at the Kolkata Port Trust in the eastern state of West Bengal says another two crew members were being treated Tuesday at a Kolkata hospital. The official spoke on condition of anonymity because he was not authorized to speak with media.

The victims were found Sunday aboard the Chinese-built carrier Tuo Fu 3 anchored near Haldia city in the Bay of Bengal. The Indian official said the victims had reportedly collapsed immediately after entering the cargo hold filled with coal and accumulated methane gas.

The ship had been delivering the coal to India’s state-owned National Thermal Power Corporation.