Four people were killed and five others were in critical condition after a drive-by shooting at a streetside bar in Puerto Rico, police said Tuesday. Authorities believe the shooting late Monday is tied to drug trafficking.

While Puerto Rico has long served as a transit point for multimillion-dollar drug shipments out of South America, drug-related shootings involving multiple victims are considered rare. The shooting raises concerns that this could change.

DRIVE-BY SHOOTING IN PUERTO RICO KILLS 5, INCLUDING A TEENAGER

Police said in a statement that unknown suspects in a moving car opened fire in the northern town of Toa Baja. Two men and two women were killed, and three women and two men were hospitalized. Among those in critical condition was the brother of the former mayor of the coastal town of Cataño, according to police.

Authorities said a 35-year-old suspected drug dealer killed in the shooting appeared to be the target.

No one has been arrested.

At least 74 killings have been reported on the island of 3.2 million inhabitants this year, six more than in the same period last year.

Last month, four men and a 16-year-old boy were fatally shot along a highway in another drug-related attack in the eastern town of Ceiba.