The owner of a neighborhood bar and grocery where seven people were shot to death has been arrested and charged with drug trafficking, federal authorities said Tuesday.

The arrest of Wilfredo Semprit Santana appears to support official suggestions that the Oct. 17 shooting was linked to a battle over drug trafficking.

Semprit was indicted Tuesday on one count of conspiracy to possess with intent to distribute substances containing heroin, cocaine, crack cocaine and marijuana, U.S. Attorney Rosa Emilia Rodriguez said.

It was not immediately known whether Semprit had an attorney. An official with Puerto Rico's public defender office said it was not clear if he had been assigned an attorney.

If found guilty, Semprit could face between five to 40 years in prison and up to $2 million in fines.

Police say at least two men barged into the La Tombola bar in Toa Baja, just west of San Juan, and opened fire on a crowded party marking the bar's reopening. At least seven people were killed and 20 injured, including a 9-year girl and a pregnant woman who lost her 8-month-old fetus.

Police said at least five different types of bullets were found at the scene, indicating some of the people in the bar exchanged fire with the attackers.

Initial efforts to investigate the shooting were hindered because witnesses feared to describe the killers, authorities said.

Police had strengthened security at a hospital where the wounded were recovering after the shootings, following anonymous threats that more people would be killed.

Rodriguez said the arrest, the first in the case, should help alleviate fears of more shootings.

"We will continue working...to prevent further senseless acts of violence which have become all too common in Puerto Rico," she said.

More than 700 people have been killed this year in the U.S. Caribbean territory, and the police chief estimates that 70 percent of killings are tied to drug trafficking.

The U.S. Drug Enforcement Administration is helping with the investigation, said Special Agent in Charge Javier Pena.