A half-dozen people in St. Mary’s County have recently received phone calls in which a man claimed that their relatives would be held captive until money was wired to him, authorities said.

The sheriff’s office in the southern Maryland county said law enforcement received six calls Monday from people who had received similar demands. The office described the demands as part of a scam, similar to extortion schemes that have been reported in recent months in several parts of the county.

According to the sheriff’s office, the targets of the scam were told that a family member had been in a car collision with a relative of the man who was calling them.

The caller, according to the sheriff’s office, told potential victims he was “holding their relative captive” until he received the amount of damages caused by the collision.

The calls all came from a 301 exchange, and the so-called car damage ranged from several hundred dollars to several thousand.

Describing the calls as “very alarming,” the sheriff’s office said that those who are targeted should ask as many questions as possible, get in touch with relatives, and call law enforcement rather than send any money.

The calls appeared similar to those reported last year in Montgomery County in which someone claiming to be a relative, often a grandson, says he has been in an accident and needs money quickly and without fuss. Several people have described the calls as persuasive and have said the caller appears to know some family information.

In West Virginia, the state police warned last year against a telephone scam in which callers claimed to be state police officers and asked that money be wired to them.

The scams also appeared similar to one described by the FBI in 2010.

In a posting on a Web site devoted to computer scams, the FBI said that in a common scheme, people were notified that a friend or relative needed money immediately after being robbed in a foreign location.

The message imparts a sense of urgency that may overcome skepticism, the FBI said.