A senior American official has told CNN that intelligence reports received from various US agencies indicate that Iran's air defense systems have been on high alert in the last few days.
The report follows several mysterious fires which broke out in locations in the Islamic Republic.
According to the official quoted, Iranian air defense batteries have been readied to launch surface-to-air missiles immediately upon detection of a threat.
The official declined to say how the US received these indications, CNN added, and several US military officials declined to comment publicly on the issue.
These incidents were the latest in a string of mysterious events, which began on June 30.
A gas explosion shook a residential building in Tehran, Iran, on Saturday, injuring one person, Iran's semi-official ISNA reported.
On Friday, IRIB reported that an explosion was heard in Western Tehran, and electricity had been cut in the area around where the explosion occurred.
Two people were killed in an explosion at a Tehran factory on July 7.
An explosion caused severe damage at the Natanz nuclear facility on July 2.
In June, an explosion near a military complex in Parchin area southeast of Tehran rocked the Iranian capital. Authorities blamed that blast on "leaking gas tanks."
13 people were killed in an explosion at a medical center in Tehran on June 30. Tehran Deputy Governor Hamid Reza Goudarzi told state TV that the explosion was caused by a gas leak.