Barack Obama has consoled the rural Texas community rocked by last week's deadly fertiliser plant explosion.

The president told mourners on Thursday that they are not alone in their grief and they will have America's support to rebuild from the devastation.

"This small town's family is bigger now," Mr Obama said during a memorial service at Baylor University in Waco for victims of the blast in nearby West, that killed 14 and injured 200.

Nearly 10,000 gathered to remember the firefighters and police killed in the blast, a crowd more than triple the size of West's entire population of 2,700.