Fourteen people were killed when a military helicopter crashed on Friday in northwestern Mexico, the navy said.

"A Black Hawk helicopter was involved in an accident, the cause of which is unknown at this time," a statement said.

It said the aircraft was carrying 15 people and the sole survivor was receiving medical treatment after the crash in the state of Sinaloa.

The helicopter went down while carrying out unspecified operational activities, according to the statement, adding that an investigation would be carried out into the cause.

The navy "mourns the death of those who lost their lives in this accident -- naval personnel, who in life showed their service and dedication to the nation," it said.

The crash was not believed to be linked to the capture Friday of a notorious drug kingpin wanted by the United States for the murder of a US undercover agent, the navy said.

Rafael Caro Quintero is accused by the United States of ordering the kidnap, torture and murder of Drug Enforcement Administration (DEA) special agent Enrique "Kiki" Camarena in 1985.

He was detained by Mexican marines in the town of Choix in Sinaloa.