Neither official provided additional details about any response plans.
The alert was sent to several federal and local law-enforcement agencies, according to one of the officials.
Customs and Border Protection declined to comment. Representatives for the Department of Homeland Security didn’t respond to requests for comment.
The Trump administration said at the end of August that four companies had been selected to build short sections of concrete border walls. Designs for four other wall samples built from “other materials” were selected earlier this month.
President Donald Trump promised to build a wall along the Mexican border the day he announced his run for president in June 2015. The pledge became a rallying cry at campaign events, along with his proclamation that Mexico would pay for the structure.
The Homeland Security Department is using money already in its coffers to pay for the prototypes.
The concrete sections of wall prototypes have an average cost of about $450,000 and will be 30 feet long and up to 30 feet high, according to Ron Vitiello, acting deputy commission of Customs and Border Protection.
The agency said earlier this month that the other designs would be between 18 and 30 feet high. It didn’t provide a cost estimate for the other wall samples.
There is already about 650 miles of fencing along the Mexican border, much of it built as part of the 2006 Secure Fence Act during President George W. Bush’s second term.
The intelligence alert said protesters have previously tried to block border fence constructions.
Officials warned that efforts to stop new border wall construction could mirror the size and scope of protests against the Dakota Access Pipeline in North Dakota.
The CBP alert also warned law-enforcement officials that drug cartels and other criminals could try to take advantage of any chaos created by the protests to commit crimes along the border.