Story highlights The phone didn't contain evidence of contacts with other ISIS supporters

The mystery of the missing 18 minutes remains unsolved

(CNN) Hacking the San Bernardino terrorist's iPhone has produced data the FBI didn't have before and has helped the investigators answer some remaining questions in the ongoing probe, U.S. law enforcement officials say.

Apple and the FBI are squaring off again Tuesday in testimony at a House hearing on encryption, with the recent battle over unlocking a terrorist's phone looming in the background.

Investigators are now more confident that terrorist Syed Farook didn't make contact with another plotter during an 18-minute gap that the FBI said was missing from their time line of the attackers' whereabouts after the mass shooting, the officials said.

'No evidence' of ISIS contact

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The phone has helped investigators address lingering concern that the two may have help, perhaps from friends and family, the officials said.

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