Terrorist threats against several airports — Los Angeles International Airport, London’s Heathrow and New York’s JFK — were posted to what has been identified as a pro-Islamic State Twitter account ahead of what is supposed to be a record-breaking fourth of July weekend for travel out of LAX.

Counterterrorism organization SITE Intelligence Group raised the alert about the threat against planes “flying from (London’s) Heathrow (Airport) to the US” over the 4th of July weekend, according to the Los Angeles Times. The message added: “there will be a device placed in either Heathrow, LAX or JFK Airports.”

Authorities cast the threat as not credible, but nonetheless insisted they take threats seriously. Similar threats are said to come in frequently around busy travel holidays and when other attacks have occurred, the Times reported.

Security had already been boosted at LAX for the holiday weekend, following an Islamic terror attack on the Istanbul airport in Turkey. The security boost reportedly involves LAX police, federal agencies, the Los Angeles Police Department and the L.A. County Sheriff’s Department.

LAX travelers speaking with local KTLA news expressed ease and had no worries about their safety. The Times reported that a record 1.2 million people are expected to make their way through LAX over the holiday weekend.

Travelers may notice the increased law enforcement presence, as well as tactical vehicles around the airport like those seen Friday, according to the report. The FBI was cited as saying on Thursday that there are no known credible threats to the U.S. over the weekend.

In addition, Reuters reported that British Transport minister Lord Ahmad of Wimbledon urged caution, encouraging vigilance to terrorist threats among the British public. That report noted that “[t]he absence of known threats does not ensure safety” before citing Orlando’s Islamic terror attack.

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