What to Know The Bucks County DA is warning residents in the greater Quakertown area to look out for suspicious devices.

There may be four bombs hidden in the area, the Bucks DA said. The warning is tied to the investigation of some 30 mystery blasts nearby.

David Surman, Jr., faces a litany of charges related to the case including possession of a weapon of mass destruction.

As many as four explosive devices could be hidden around the Quakertown area, Bucks County's district attorney says.

Matt Weintraub, the Bucks County DA, put the public on notice Tuesday as a precaution, he said, in case a resident came across one of the devices.

"This is just to caution the public. This is an FYI, not an S.O.S.," Weintraub said.

Authorities are concerned the devices could be in the Milford Square and Revere sections of Upper Bucks County.

"They may not be able to be detonated at all, but they may," the DA told NBC10 Tuesday evening.

The warning comes as prosecutors and federal agents continue to investigate a series of explosions that took place over several months in the greater Quakertown area.

In late June, local and federal authorities including the ATF and FBI arrested David Surman, Jr. on accusations he built and detonated explosives in the Upper Bucks County area. Between April and June, at least 30 explosions were reported by residents. Some left craters on roadsides and in farmlands. Residents were rattled and investigators befuddled for weeks.

Detectives found multiple explosive devices in Surman's Milford Township home when he was taken into custody on June 28. At least one device was large enough to create mass destruction, according to authorities.

The 31-year-old also owned a chemical and solvents business and was, according to authorities, in possession of methamphetamine. His girlfriend, Tina Smith, was charged as an accomplice in the explosive case on early October.

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Surman also hit more legal trouble earlier this month when he was charged with possession of child pornography.

Surman faces a Nov. 2 formal arraignment in the explosives case.

Some of the seized explosive devices were constructed of small plastic canisters. A larger device was wrapped in electrical tape and had a unhappy face emoji bomb pasted to the side.

Weintraub said there's been no recent reports of explosions in the area, but would not elaborate as to what prompted the alert. He did say there was credible evidence worth speaking out, however.

The warning has definitely gotten the attention of residents like Kevin Willauer, who owns a farm in Milford Township. He's already warned his son to take extra care when riding his dirt bike around the family's land.

And while authorities have not received new reports of explosions, Willauer said he's heard loud booms recently.

"I've definitely heard loud explosions over the past couple of weeks, and was asking family and friends if they heard them as well. I don’t know if it was related to it or not," he said.

Anyone who comes across a suspicious looking device is advised not to touch it and instead back up and dial 911.