Law enforcement officials say they have no way of knowing how many attempts have been successful, but the warden of the Lee Correctional Institute, Cecilia Reynolds, said that in recent weeks her officers found 17 phones in one inmate’s cell. She said she suspected that the phones continue to come in on drones.

“We’ve got to do something about this — these cellphones are killing us,” she said.

Smartphones are so desirable to inmates because unlike pay phones at prisons, they are not recorded or monitored. The phones also allow them to watch pornography and communicate surreptitiously with fellow prisoners.

The phones are essential for coordinating with smugglers using drones, because the prisoners need to know where to find the deliveries in the yard. The prisoners can then use the phones to quickly pay their suppliers.

The problems that cellphones create were exposed in February during a nine-hour riot at the prison here in Bishopville. Inmates took control of a part of their dormitory after they stabbed two officers and assaulted three others. Before the authorities could regain control of the facility, the inmates called a local television station from their cellphones, claiming they were holding other inmates hostage. The inmates then sent the television station photos of the hostages and the destruction they had done to the dorm.

Ever since a hobbyist drone crashed on the South Lawn of the White House in January, there has been an increased push by law enforcement agencies, companies and privacy watchdogs to come up with ways to restrict the flight of drones. That task has been particularly difficult because the laws and regulations that govern drones are outdated and confusing.

“It’s a new area and we don’t know the full extent of drones’ capabilities — both good and bad — and because of that we don’t know what the gaps are in the laws and what we need to do to clarify them,” said Lisa Ellman, who helps lead the unmanned aircraft systems practice group at the law firm McKenna, Long & Aldridge in Washington.

Nets cannot be built over every sensitive location in the United States to keep drones out. So, for now, the best way to control the problem appears to be “geofencing” software that prevents the drones from flying over a specific location.