(Adds tolls, police comment)

DHAKA, June 2 (Reuters) - Blasts at a multi-storey hotel in the Bangladesh capital overnight killed a man and injured nearly 30 others, police and fire authorities said on Monday, adding the explosions appeared to have been caused by gas leaking from a room heater.

They said two explosions rocked the nine-storey Orchard Plaza hotel in Dhaka's Nayapaltan area late on Sunday night, setting two upper floors on fire.

A Bangladeshi hotel staff member died at a hospital later on Monday and at least two other locals were in serious condition, police said.

Firefighters said both blasts were apparently caused by gas explosions. "It's not a bomb," a fire official told reporters.

"It is not a sabotage. There was no trace of explosives," Naeem Ahmed, commissioner of Dhaka Metropolitan police told a news conference after an investigation.

In recent years Bangladesh has been repeatedly hit by bomb blasts, mostly blamed on Islamist militants, which have killed dozens of people and injured hundreds.

One of the injured was a Sri Lankan national who told the police there was an explosion just as he lit a cigarette in his room.

"The gas might have leaked from a heater at a room on the 6th floor where the Sri Lankan was staying," Police Inspector Farid Ahmed said.

A Nepali hotel guest said the second blast occurred three-and-a-half hours after the first one, and was much bigger.

The injured were being treated at hospitals for multiple burn injuries. There were guests from Singapore and India as well.

"We are checking the whole place. Bomb or gas, it's a serious incident and we are taking it seriously from a security point of view," said a senior police officer on the scene.

Ashish Chokhani, a Nepali citizen in Dhaka on a business trip, said the first blast took place at about 9:15 p.m. (1515 GMT) on the sixth floor of the hotel.

"I ran out of my room and went down, and came back after some time. At around 11:30 there was a bigger blast on the hotel roof and the hotel was immediately vacated," he said.

"People were saying the blasts were caused by leakage in gas pipelines on the roof and there was a big fire," Chokhani told Reuters by telephone. (Reporting by Anis Ahmed, Nizam Ahmed and Ruma Paul; Editing by Jerry Norton)

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