HOPEWELL, Va. (NewsNation) — Authorities Monday continued to search for four inmates who escaped from a Virginia federal prison’s satellite camp over the weekend.

Inmates Corey Branch, Tavares Lajuane Graham, Lamonte Rashawn Willis and Kareem Allen Shaw were discovered missing from the Federal Correctional Complex Petersburg’s satellite camp in Hopewell, Virginia, around 1:45 a.m. Saturday, the Federal Bureau of Prisons said in a news release. The minimum security facility houses 185 male offenders, officials said. Officials did not release any details about how the inmates escaped.

The prison website said its satellite camps around the county, which are often adjacent to or adjoining to the prison’s main building, provide inmate labor to the main institution and to off-site work programs.

Branch, 41, was sentenced in the Eastern District of Virginia to more than 13 years for possession with intent to distribute fentanyl and felon in possession of a firearm. Graham, 44, was sentenced in the Eastern District of North Carolina to 10 years for possession with intent to distribute 500 grams or more of cocaine and 28 grams or more of cocaine base, and possession of a firearm in furtherance of a drug trafficking crime.

Willis, 30, was sentenced in the Eastern District of Virginia to 18 years for possessing and concealing a stolen firearm and possession of a firearm by a convicted felon. Shaw, 46, was sentenced in the Western District of Virginia to more than 16 years for conspiracy to possess with intent to distribute a measurable quantity of heroin.

The U.S. Marshals Service, the FBI and other law enforcement agencies were notified and an internal investigation underway, officials said.

This escape comes after convicted murderer Gonzalo Lopez escaped from his Texas prison van last month, then killed a grandfather and his four grandsons. On May 12, Lopez broke out of his restraints and cage, stabbed the bus driver and sparked the largest manhunt in Texas history. In response, Texas officials had stopped all non-emergency inmate transportation. Law enforcement officers shot and killed Lopez in South Texas earlier this month.

The Associated Press and NewsNation affiliate WRIC contributed to this report.