The firm that unlocked the iPhone of a San Bernardino shooter is not, as previously reported, Israel’s Cellebrite but its identity may remain secret, according to media reports.

Obama administration officials said the firm concerned has sole legal ownership of the technique, making disclosure “highly unlikely”, said Reuters. The officials said the firm was non-US but declined to provide further details.

The White House previously established a process in which it weighs whether to disclose any security vulnerabilities it finds but that process does not cover techniques owned by private companies.

The sources also said the FBI itself probably does not know how the technique works, further shrouding the whole episode in mystery.

The government and FBI have faced calls to share the hack so Apple can create a patch for it.

Back in February, the FBI said it was unable to access the iPhone 5c used by one of the San Bernardino shooters without help from Apple. The law enforcement agency won a court order to force the company to break into its own device. But Apple, with the backing of leading tech firms, resisted.

However, the FBI dropped the case, the day before a vital court hearing, saying it had found a way to crack the iPhone’s encryption, although it seems the technique will not work on more recent models.

Earlier in the week, The Washington Post reported that the FBI paid professional hackers a one-time fee to access the iPhone in question. According to sources, the FBI did not turn to Cellebrite to crack the iPhone but instead used the hackers.