SAN DIEGO (Border Report) — Mexican nationals are more likely to be detained after being apprehended by federal immigration officers, according to data compiled by the Transactional Records Access Clearinghouse.

TRAC figures show that in July, 57 percent of Mexican nationals arrested for crossing the border or for being in the country illegally were held in detention centers while their proceedings take place in immigration court.

By contrast, overall, only 30 percent of migrants were detained after their apprehensions.

According to TRAC, ICE determines when a person is held, and that there is no specific pattern in the decision-making.

“In reality, little is known about the factors that influence these custody decisions,” writes TRAC. “The ICE agents have wide discretion to make decisions and their criteria is rarely revealed.”

According to TRAC, it appears decisions are taken by the agents themselves and are influenced by their own backgrounds and ethnic identity.

However, the state in which migrants are apprehended can also determine whether they are detained.

TRAC says being detained can have major implications, adding that individuals who remain in custody have a more difficult time obtaining the documents and the legal help to make a case against deportation.

TRAC also says that the vast majority of individuals in ICE custody, through June 30, had no criminal record, and that 4 out of 5, either had no record or had only committed a minor offense such as a traffic violation.