A 7-year-old boy is missing after the van attack in Barcelona that left 13 dead and more than 100 others wounded, his family announced Friday.

The grandfather of Julian Cadman said the young boy went missing after becoming separated from his mother, who was seriously wounded in the attack.

"We have found Jom (my daughter-in-law) and she is serious but stable condition in hospital," the boy's grandfather, Tony Cadman of Sydney, Australia, wrote on Facebook.

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He added, "Julian is 7-years-old and was out with Jom when they were separated, due to the recent terrorist activity. Please share if you have family or friends in Barcelona."

***MISSING IN BARCELONA*** My Grandson, Julian Alessandro Cadman is missing. Please like and share. We have found Jom... Posted by Tony Cadman on Thursday, August 17, 2017

The Facebook post had nearly 80,000 shares and 8,000 likes as of Friday morning.

British Prime Minister Theresa May told Sky News that officials were "urgently looking into reports of a child believed missing, who is a British dual national." May did not identify the boy.

"The Foreign Office is offering consular assistance to those who were involved in the attack and their families, and are working urgently to see if there are others who need their help," May added.

Citizens from at least 24 countries were among those killed and wounded in Barcelona, the Catalan regional government said Thursday.

Three people were arrested following the deadly attack, but the driver of the van remains at large. The Islamic State of Iraq and Syria (ISIS) have claimed responsibility for the attack.

U.S. law enforcement officials told CBS News there is intelligence that indicates the Barcelona attack was more than just an ISIS-inspired attack.

CBS News national security analyst Fran Townsend said the attack looks like it was "much more directly controlled than merely inspired."

"As you look at the chronology, this was a fairly large cell, had to have been in place for a while -- pretty good planning," Townsend said on "CBS This Morning." "You had the house that blew up when they failed to put together these gas canisters -- probably for a car bomb. Then you had the tragic sort of seven-block rage of this car killing 14. You also had in Cambrils last night another car attack."