April 27 (Bloomberg) -- Mexicans in Arizona should carry documentation and “act carefully” after the state passed a law requiring local police to determine the immigration status of anyone suspected of being in the country illegally, Mexico’s Foreign Ministry said.

The ministry said the warning is directed toward Mexicans living, studying or planning to travel to the southwestern U.S. state, which shares a border with northern Mexico, according to the e-mailed statement sent today. It comes as members of U.S. President Barack Obama’s administration said they have concerns about the new law and may seek to overturn it in court.

“There is an adverse political environment for migrant communities and all Mexican visitors,” Mexico’s ministry said. “It’s important to act carefully and respect the local laws.”

The Arizona law makes it a state crime to be in the U.S. without proper documentation. The state has an estimated 460,000 residents living there illegally, the seventh highest total in the country, according to the U.S. Department of Homeland Security. Opponents say it will lead to discrimination and racial profiling by law enforcement authorities.

Arizona Governor Jan Brewer, who is running for re- election, signed the bill into law on April 23, saying it would address problems of violence along the border with Mexico and crime due to illegal immigration while protecting individual rights.

‘Murderous Greed’

“We cannot sacrifice our safety to the murderous greed of drug cartels,” Brewer said. “We cannot delay while the destruction happening south of our international border creeps its way north.”

Homeland Security Secretary Janet Napolitano said during congressional testimony in Washington today that her agency has “deep concerns” about the law and that it will “detract from and siphon resources that we need to focus on those in the country illegally who are committing serious crimes.” U.S. Attorney General Eric Holder said today that the Justice Department may go to court to challenge the statue.

The law, which goes into effect 90 days after the Arizona legislative session ends, states that police must investigate if they have “reasonable suspicion” that someone is undocumented, according to Gabriel Chin, a professor of Law and Public Policy at the University of Arizona in Tucson. Police officers may face lawsuits if they fail to do so, he added.

‘Angered and Saddened’

“It’s very hard for me to see how this law can be enforced without discrimination,” Chin said in a telephone interview today from Tucson. “It seems to be inevitable.”

Mexican President Felipe Calderon said April 26 that his country’s citizens are “angered and saddened” by the Arizona law, which he said “doesn’t adequately guarantee respect for people’s fundamental rights.”

About a quarter of Arizona’s 6.6 million residents are of Hispanic descent, according to the U.S. Census Bureau.

U.S. Democratic Party leaders said last week that an overhaul of immigration law could advance through Congress this year if Senate Majority Leader Harry Reid can pick up enough support to muscle it through the Senate first, according to April 22 remarks by Reid and House Speaker Nancy Pelosi.

Pelosi told reporters that she will find the votes for the measure in the House -- where Democrats have 254 of 435 seats -- if the Senate can clear it.

Senator Lindsey Graham, a South Carolina Republican who has been working with Democrats on an immigration overhaul, said rushing legislation this year would be a mistake because it doesn’t have the votes yet to pass.

“The worst thing we could do is bring up immigration reform and have it crash and burn politically,” he told Napolitano. “If immigration comes up this year, it’s absolutely devastating to the future of this issue.”

To contact the reporters on this story: Jonathan Levin in Mexico City at jlevin20@bloomberg.net; Catherine Dodge in Washington at cdodge1@bloomberg.net