According to US-based media, citing the source, the FBI is combining resources from neighboring satellite offices in Texas and assets are on standby to assist, should the state request.
Earlier on Saturday, a man opened fire at a Walmart in the Cielo Vista Mall in El Paso, Texas. According to the state's governor, 20 people were killed and 26 were injured in the massacre.
El Paso Police Chief Greg Allen told reporters that the incident may be classified as capital murder and a hate crime.
The incident occurred just six days after at least 15 people were injured and four people were killed - including two children - during a shooting spree at an annual family festival in the California town of Gilroy.
Both gunmen reportedly used AK-47-type military assault rifles. There has, however, been no direct link to connect the two massacres, according to media reports.
Local media said earlier that the El Paso shooter had posted a manifesto online before attacking people in the Walmart. This manifesto was cited by US-based media outlets as being similar to a screed written by an Australian gunman who in March killed 50 people in the city of Christchurch, New Zealand, in a series of mosque shootings.