Illegal immigrants from Mexico, Honduras and Guatemala successfully crossed the Texas border but later were killed in a car crash.
A fourteenth person died after the crash of a pick-up truck overloaded with illegal immigrants in South Texas.
U.S. Immigration and Customs Enforcement spokesman Greg Palmore said that nine people remain hospitalized after the latest death.
Palmore said the 11 men and three women who died included illegal immigrants from Mexico, Honduras and Guatemala.
The accident occurred in the rural county of Goliad, about 90 miles southeast of San Antonio on Sunday night. Authorities say 23 people were packed into the van when it veered off the road and crashed into trees.
Police are still investigating the crash. The identities of those killed are still unknown.