Scientists have expressed doubt that a man in Tamil Nadu, India, was the first person to have been confirmed killed by a meteorite strike, as the state's top official has declared.

"Initial assessments, based on photos posted online, are not consistent with something from space. Small meteorites do not start fires or cause explosions when they hit the ground. To form a crater the size of what has been posted online would have required a meteorite of at least several kilograms," NASA said in a statement.

"While more details may be forthcoming from local scientists, this is unlikely something from space."

Indian scientists have expressed similar doubt about their nation's claim. 

Experts said the small crater, the absence of a sonic boom before impact, a lack of debris and the green and blue colour of rock recovered from the scene suggest some other cause.

"It is highly improbable, but we will only be absolutely sure after a chemical analysis," said V. Adimurthy, a senior scientist at India's space agency.

The mysterious event has triggered an international debate about whether a meteorite, space debris, leftover explosives or even frozen waste from a plane passing overhead may have killed the man.

The meteorite attribution was announced this week by Chief Minister Jayalalithaa Jayaram, a former film star who is known for her authoritarian style.

A bus driver was killed by the meteorite at an engineering college in the state, she said, and awarded a sum of 100,000 rupees ($2,052 Cdn) in compensation to his family.

"A meteorite fell within the college premises," she said.

State officials tight-lipped

Jayalalithaa has a cult-like following in her state, with her pictures on prominent display in the offices of her party's politicians, as a sign of their unquestioning loyalty. Since her comments, state officials have been reluctant to discuss publicly what happened.

A team of scientists from the Indian Institute of Astrophysics in Bangalore arrived in Tamil Nadu on Tuesday to inspect the two metre-wide crater and collect the recovered rock sample, which is small enough to fit in a hand. 

G.C. Anupama, an astronomy professor at the institute, said the probe would focus on the chemicals in the debris, as meteorites have high iron levels. She declined to comment whether she believed the debris was a meteorite.

C.B. Devgun, who has been tracking meteorites for the last two decades, said the colour of the rock and absence of other particles ruled out a meteorite.

'It cannot be a meteorite'

"It cannot be a meteorite," he said. "It was a greenish colour and no other pieces of debris were found. Normally it would be a darkish yellow or darkish black in colour, just like burned coal, with a slightly melted surface."

The last reported death from a meteorite strike was in 1825, according to a list maintained by International Comet Quarterly, a scientific journal.

In 2013, a meteorite that exploded over central Russia rained down fireballs and caused a shock wave that smashed windows, damaged buildings and injured 1,200 people.

With files from CBC News