Nine bodies were found Thursday in the border city of Tijuana while seven alleged Gulf cartel hit men were behind bars in Mexico City.

Eight of the bodies found in Tijuana were dumped face down in an empty lot near a day care center. Their hands were tied and a message nearby read: "Here are your people." The site was littered with shell casings.

The ninth body was found wrapped in a sheet in another section of the city.

An official for the state prosecutor's office said the killings were believed to be tied to drug cartels fighting each other for control of Tijuana.

About 30 people have been killed in drug-related violence in the past week in the border city, including what appeared to be the remains of two people stuffed in a barrel and dissolved with acid. Officials were still running tests on the barrels' contents to confirm them as human.

In Mexico City, an anonymous tip led police to a downtown restaurant where seven alleged members of the Gulf cartel's infamous Zetas hit men were arrested, according to a statement issued late Wednesday by the federal Attorney General's office.

Officials gave no other details, but Mexican media reported the suspects were taken into custody at Los Arcos seafood restaurant in Mexico City's touristy Zona Rosa section.

The Zetas were initially formed by an elite group of Mexican army deserters and have grown to become Mexico's most infamous and feared hit men.

Three other alleged Zetas were recently arrested for throwing grenades that killed eight people at an Independence Day celebration in the western city of Morelia.