The phrase "alert was believed" is correct and usable in written English.
It can be used in contexts where someone is expressing that a certain alert or warning was thought to be true or credible.
Example: "The emergency alert was believed to be a false alarm until further investigation confirmed its validity."
Alternatives: "alert was thought" or "alert was considered".
Such alerts are believed to be relatively common and many companies have policies and practices in place to handle updates and changes.
It was believed the arrest was linked to a security alert in Larne, County Antrim.
They've now reformed and, if Google Alerts are to be believed, are tonight playing in London's Dalston as part of their UK tour.
That appears to have alerted Los Che, who are believed to have already started the process of raising the £25m they feel will be enough to see Mata return to the Mestalla, with sponsors and local businesses set to fund the bid.
Users can choose to receive an alert when certain people are believed to be nearby.
An alarm on Good Friday is believed to have alerted police - but it was judged to require no further response.
Borussia Dortmund striker Robert Lewandowski, 24, is ready to quit the German club in the summer, alerting Manchester United who are believed to be interested in the Pole.
The United States Embassy cautioned Americans in Uzbekistan to be on "highest alert" and said, "Other terrorists are believed still at large and may be attempting additional attacks".
Authorities in Washington state say they have issued an Amber Alert for an endangered newborn who is believed to be with his drug addicted mother.
The Iranian government put its military on high alert immediately after the strikes, but is believed to be awaiting a visit tomorrow from the Russian President, Vladimir Putin, before taking any retaliatory action.
It is these monitoring systems that are believed to have alerted Tesco to the problems that led to it suspending the site and halting transactions.
