VERACRUZ, Mexico (AP) " Federal investigators questioned 48 Veracruz city traffic officers Wednesday about the disappearance of the top customs official for one of Mexico's most important ports.
Customs administrator Francisco Serrano has not been seen since his smashed government vehicle was found abandoned at an accident scene three days ago, Veracruz state prosecutor Salvador Mikel said. Serrano recently launched a new system to check shipping containers at the Gulf coast port in Veracruz, which has seen increasing drug violence in recent years.
Investigators decided to question the officers, who were on duty when the crash happened, after viewing footage from street security cameras, Mikel said. Gunshots are heard in the video, which shows the arrival of transit agents who did not report the accident, said Francisco Portilla, the state government's deputy secretary.
At least 41 of the officers were released Wednesday, with the rest still being questioned. Prosecutors said none of the officers has been charged with a crime or labeled a suspect.
Mexican drug gangs often buy off or blackmail police into cooperating. President Felipe Calderon's government has stepped up its campaign to fight corruption in recent weeks, arresting dozens of police and officials in several states " including 10 mayors in his home state of Michoacan " on suspicion of collaborating with drug traffickers.
Soldiers raided police stations in the northern state of Nuevo Leon for a third day Wednesday, detaining six more officers for questioning. More than 60 officers have been detained in the operation, which began after lists with the names of police were found in possession of suspected drug dealers arrested in May.
The arrest of the mayors has drawn accusations that Calderon is using his fight against drug cartels for political gain ahead of the July 5 legislative elections, allegations the federal government has denied.
On Wednesday, thousands of people marched in Mexico City to demand the release of the mayors, most of whom belong to opposition parties. The demonstrators, dressed in white, held up signs reading "We trust you" and "We know you are innocent."
More than 10,750 people have been killed in drug violence since December 2006, when Calderon launched an offensive against cartels that has grown to include more than 45,000 soldiers deployed across Mexico.
Alex Alvarez, the assistant attorney general of southern Tabasco state, resigned Wednesday, a week after surviving an attack that killed a bystander and injured 13 other people. After attacking the prosecutor's vehicle, a convoy of armed men continued to toss grenades and shoot at officers in a midnight chase through the Gulf state's capital, Villahermosa.
On Tuesday, several banners appeared in the city, purportedly signed by the Gulf cartel, accusing Alvarez of protecting drug traffickers. Tabasco Gov. Andres Granier told reporters Wednesday that he did not believe Alvarez was involved with drug gangs.
Alvarez told a local radio station that it was a family decision that he resign after the attack.
As federal forces were rounding up the transit officers in Veracruz Tuesday, a state police officer and his bodyguard were found fatally shot in the head in the Veracruz town of Catemaco. The town's police chief, Silvio Reyes, blamed drug gangs.
Three other police officers were killed in separate attacks between Tuesday and Wednesday in Ciudad Juarez, a town across the border from El Paso, Texas.
On Monday, the body of a U.S. legal resident, Li Huang Liang, was found in Tijuana. Liang lived across the border in Chula Vista, California. Authorities said he was stabbed multiple times and hit over the head, but could have been killed in Chula Vista and dumped in Tijuana.