Drug enforcement officers in the US say they have arrested more than 2,200 people in an investigation targeting Mexican trafficking rings.

美国毒品稽查官员称，在一场针对墨西哥毒品交易链的调查中，他们已逮捕2200多名疑犯。

The joint operation lasted almost two years and culminated（达到高潮） on Wednesday with more than 400 arrests across 16 states.

Officers also seized considerable amounts of methamphetamine（甲基苯丙胺） , marijuana（大麻） and heroin.

US Attorney General Eric Holder said Project Deliverance had been a significant blow to Mexican cartels.

He said the arrests and seizures would disrupt their operations but also warned that it was only one battle in an ongoing war.

The investigation focused on the infrastructure used to distribute（分散，散布） illegal drugs across the US and smuggle（走私） guns and cash back to Mexico.

During the 22 months the operation lasted, officers seized more than $150m (£103m), 2.2 tonnes of cocaine, half a tonne of methamphetamine and 62 tonnes of marijuana.

Mr Holder said it had been the most extensive and most successful law enforcement effort to date targeting Mexican drug cartels.

Expanding criminal net

A recent report by the US justice department suggested Mexican criminal groups had expanded their activities in the US with heroin production doubling in 2008.

In its National Drug Threat Assessment, the justice department said trade in marijuana, ecstasy（入迷，狂喜） and methamphetamine had also grown.

The report found that Mexican groups were active in every region of the US.

Michele Leonhart, acting head of the US Drug Enforcement Administration, said Project Deliverance had not been just about cutting off the supply of drugs entering the US, but also shutting down the flow of drug profits and guns to Mexico.

Mexican President Felipe Calderon told a joint session of the US Congress in May that Mexico needed help from its northern neighbour to tackle organised crime.

More than 22,000 people have been killed in Mexico since Mr Calderon came to power, most of them in drug-related gun battles.

Mr Calderon has blamed the lifting of a ban on US assault weapons ban in 2004 for an increased flow of guns across the border.

He said that he was confident his country would win its fight against drug gangs with US cooperation.

Attorney General Holder praised the role of Mexican law enforcement officers in Project Deliverance and the arrest by Mexican officials on 30 May of Carlos Ramon Castro-Rocha.

Mr Castro-Rocha has been indicted（控告，揭发） on drug trafficking charges and US officials accuse him of being the leader of the Castro-Rocha cartel.