Residents in the Bellevue neighborhood Richmond Virginia's North Side were shaken and stirred yesterday by another mysterious boom.

The explosion was heard around 9:49 a.m. and prompted at least 35 calls to 911, said Richmond fire Lt. Keith Vida.

Reports placed the origin of the boom in the 1400 block of Wilmington Avenue.

Officials were unsure what caused the explosion. Vida said investigators searching the area were unable to find evidence of the household materials used in a number of the chemical-reaction explosive devices detonated in the area in the past month.

Two Ginter Park teenage boys have been arrested in connection with several of the explosions. Officials have said they are considering felony charges against four more suspects. Simply making or possessing the explosive devices is considered a crime.

To date, the booms have not injured people, nor have they caused serious damage to property. However, a number of homeowners in the area have reported cracks in their walls they attribute to the explosions.

Still, authorities are not convinced all of the booms can be accounted for by pranksters.

The city is expected to bring in special equipment over the next couple of days to help monitor the ground for possible seismic activity.

"We want to look above and below ground," Vida said. "We will continue the investigation."

Jim Nolan is a witer for the Richmond Times Dispatch.