A tip from a concerned citizen that multiple bombs were kept in a house led to multiple agencies descending on a Grass Valley neighborhood Saturday afternoon.

Dispatchers received a 911 call just after 3:30 p.m. that there were a number of bomb devices in a residence in the 400 block of Lamarque Court, off Brighton Street between Condon Park and the fairgrounds.

The caller was contacted and had credible information about a destructive device, said Grass Valley Police Sgt. Brian Blakemore.

An officer was dispatched to the residence and contacted a woman identified as Mary Lee Dalton, 52, who was the only person inside the house, Blakemore said,

“She quickly became less than helpful,” he said, adding the officer detained Dalton at the scene and requested additional units respond.

When Blakemore arrived along with other officers, Dalton became more forthcoming, directing them to a closet in the master bedroom.

Inside the closet, officers discovered a box with multiple plastic bags wrapped up and tied. They carefully untied one of the bags and could see two devices inside, which were photographed.

“It looked like there were at least two devices taped with electrical tape to bottles that contained some sort of suspected incendiary liquid,” Blakemore said, adding officers could also see a length of fuse cord.

“It was the kind you would find with commercial-grade fireworks,” he said. “A light-and-run type cord.”

Blakemore said that after reviewing the photographs, the police department felt the explosive devices were safe in their current state and they did not need to evacuate the neighborhood. Placer County’s Explosive Ordinance Disposal team was contacted and reviewed the photos as well.

The explosives experts advised Grass Valley Police to contact the residents in the perimeter and have them shelter in place.

Bombs were being stockpiled

The team arrived a little after 4:30 p.m. and took X-rays of the devices. According to Blakemore, they did not want to unscrew the caps on the bottles due to concerns that a spark could set them off. The squad members suited up and removed the box from the residence by hand, then used a bomb robot outside to move the box to the backyard, dump out the contents and sever the pipes from the bottles. Once that was done, they used a shotgun-type round to dismantle the devices, Blakemore said.

“They also found three additional smaller bombs that had been constructed from carbon dioxide containers and gunpowder,” he said. “Those had to be collected into a bomb box and taken offsite to be destroyed.”

Grass Valley Fire department officials collected a sample of the liquid in the bottles and it was confirmed to be flammable, Blakemore said.

The house was cleared by about 11 p.m., and the investigation is continuing.

Dalton told officers she had found the devices in a common area of the residence, put them in bags and placed them in her closet.

“We’re still looking into who constructed the devices,” Blakemore said, noting that Dalton was renting out bedrooms in the residence to a number of people, some of whom have criminal histories. “We’re confident we can link any other (involved) parties to the devices.”

Dalton was charged with felony possession of a destructive device. She was booked into the Nevada County jail in lieu of $10,000 bail.

Blakemore said there was no known target.

“They were stockpiling devices for some unknown future use,” he said. “Based on what OED said, if the devices had gone off in place, they could have gone through the exterior wall and through the wall of the adjacent house. They were highly destructive — they could have caused serious damage.”

Contact reporter Liz Kellar at 530-477-4236 or by email at lizk@theunion.com.