The Philippines has ordered tech giants Facebook, Alibaba Lazada and Sea’s Shopee to stop allowing sales of cellular equipment used for emergency messaging, after “text blasts” were used to promote a presidential election candidate.

The National Telecommunications Commission (NTC) ordered the platforms to appear before the agency on Oct. 27 to explain why they should not be held liable for allowing sales of the equipment.

The NTC’s order, made public on Tuesday, follows an investigation it ordered last week into an “emergency alert” text blast, typically used during natural disasters, that contained message of support for one of the presidential candidates.

Under local laws, the sale, manufacture and importation of equipment that can send a mass text message for free would require NTC approval.

The NTC has said the mobile text alerts must have come from illegal channels since the emergency Alert Short Message Service is used by disaster agencies.

Facebook, Lazada Philippines, Alibaba, Shopee Philippines and Shopee did not immediately respond to requests for comment.