WASHINGTON: Amid charges of racial profiling by a group of 38 civil rights organizations led by the Sikh Coalition, the US Transportation Security Administration is investigating allegations that Mexican travellers were being targeted for extra screening.

The allegations of such targeting at Honolulu International Airport "resulted in launching an immediate and thorough investigation of the behaviour detection programme at HNL," the TSA stated on Thursday.

"Pending the completion of the investigation, TSA also provided HNL Behaviour Detection Officers refresher training to ensure the programme is focused solely on identifying suspicious behaviours."

"TSA's behaviour detection programme in no way encourages or tolerates profiling," the agency said. "Profiling is not an effective form of security and our security officers are trained to treat every passenger with dignity and respect."

The statement came as 38 civil rights organizations led by Sikh Coalition called for an independent audit of the TSA to determine whether the agency engages in racial profiling.

In a letter to Department of Homeland Security Secretary Janet Napolitano, the groups expressed concern about reports that TSA officers targeted Mexican and Dominican travellers for extra scrutiny at airports in Hawaii and New Jersey.

TSA officers at the Honolulu International Airport targeted Mexicans so often that their colleagues called them the "Mexicutioners," it said.

Sikh travellers are routinely selected for secondary screening at some American airports, even after clearing advanced imaging technology machines without incident, the letter said.

The Sikh Coalition said it believes that "these troubling reports are the tip of the iceberg" for TSA profiling. "Based on Sikh experience, we've long suspected that TSA officers are engaged in a pattern of profiling minorities instead of focusing on criminal behaviour."