Two of the Trump administration’s top intelligence officials denied in a frequently contentious Senate Intelligence Committee hearing on Tuesday that classified information was shared in an encrypted group chat in which details of an attack on Yemen were discussed in the presence of a journalist who had been mistakenly added to the conversation.

Pressed repeatedly about the security breach in the previously scheduled hearing, Tulsi Gabbard, the director of national intelligence, and John Ratcliffe, the C.I.A. director, both denied that classified material had been shared in the chat in which they were included, and played down the seriousness of the revelation that it had taken place on a messaging system, Signal, not approved for such sensitive discussions