Saturday’s crash of a Russian airliner, killing 224 people on board, is being called a probable bombing by several nations, citing intelligence gathered on internal ISIS communications. The US said they had no specific intelligence prior to the incident but saw a flurry of activity in Sinai in the lead-up to the bombing.

British officials similarly confirmed their belief that the crash was likely caused by a bombing, and were the first of several nations to announce today that they are halting all flights into the Sinai Peninsula for the time being. The US isn’t banning flights, but is warning embassy employees to avoid the Sinai Peninsula pending further investigation.

Russian government officials are refusing to offer any confirmation for the reports, though the plane’s owner, Metrojet, is attributing the incident to an “external impact,” saying they are ruling out technical malfunction as a cause of the crash. Egypt’s military junta, most stubbornly, is refusing to increase security at the Sharm el-Sheikh airport in Sinai, insisting there is no proof that the plane was downed by terrorism.

That may be very much beside the point now, however, as Egypt’s tourism industry, already reeling since the 2013 military coup, seems certain to suffer another major blow with the loss of a major plane full of tourists, particularly in a likely terror attack.

ISIS affiliate in Sinai took credit for downing the plane almost immediately after it happened, though this claim was quickly dismissed by Russian and Egyptian officials as improbable. US officials, however, are now saying they intercepted private communications, which, in addition to their public claims, suggest they were something to do with the bombing.

US military satellites also detected a single “heat flash” before the plane crashed, likely an explosion. Though initially there was no way to tell if this was an accidental explosion or a bombing, the smart money now seems to be on the latter.