The mystery surrounding explosions that shook the Kincardine area last Thursday deepened yesterday with University of Western Ontario scientists ruling out a meteor shower.

"Something pretty significant exploded south and west of Goderich and Kincardine.

"It could have exploded out in Lake Huron," said Dr. Peter Brown, associate professor in the department of physics and astronomy at Western and the Canada Research Chair of meteor science.

Highly sensitive devices installed near Lucan by Western to monitor low-frequency sound waves detected a series of four impulses that lasted about a minute.

The impulses started at 11:12 p.m. on July 31.

Five minutes later, a low frequency rumbling was detected coming from the Kincardine area.

"If you had been in London and it was really quiet outside, you should just have been able to hear the low rumble from these explosions," said Brown.

"That's unusual at this sort of a distance."

With Ontario's largest nuclear plant located just north of Kincardine, the explosions have triggered inter-national media interest.

Officials at Bruce Power have said nothing unusual happened that night at the nuclear station.

South Bruce OPP were inundated with 911 calls shortly after 11 p.m. on July 31.

Residents said they witnessed shaking walls and rattling windows.

Brown said the signals detected at Lucan, probably five or six minutes after the original blast, were intense.

If it had been caused by a meteor, there should have been a bright fireball in the sky, he said.

The university has a camera system at Kincardine aimed at the sky to capture the image of any meteors.

"We have already looked during the time interval of interest," Brown said. "It was clear that night and no meteor."

The monitoring devices at Lucan indicate the explosions occurred in the same area south and west of the Kincardine area and south of Goderich.

In the past, the same instruments have picked up mining explosions in Wyoming in the western U.S. and the Shell refinery explosion in Sarnia.

"Based on frequency content and the phenomenology of the signals, these are not consistent from what we would expect from a meteor at all," Brown said.

Comment: But it does consistent, as it could be an overhead explosion.

But the signals also don't fit another theory, that it was caused by a sonic boom from a jet, he said.

"They are not all that consistent with shock waves you would see with supersonic aircraft," he said.

The closest fit for the signals from the explosion, particularly the low rumbling, would be surface blasting at a mine, Brown said.

The only mine in the area is Sifto Salt's underground operation at Goderich.

A worker at the mine yesterday who lives nearby said he has never felt any tremor from blasting at the salt mine that stretches under the lake.