SAN FRANCISCO — Technology companies, the custodians of reams of personal data from hundreds of millions of people around the world, have been under fire after recent revelations that they secretly handed over customer information, including e-mails, in response to requests by the federal government made in the name of national security.

Now, one by one, the companies are putting out data intended to reassure their users that the government gets information on just a tiny number of people. Over the weekend, Facebook and Microsoft released reports about the overall number of data requests they had received from United States law enforcement agencies. On Monday, Apple and Yahoo joined the chorus.

But rather than provide clarity, some of the disclosures have left many questions unanswered.

Apple, for example, said that from Dec. 1, 2012, through May 31, 2013, it received between 4,000 and 5,000 requests for data, covering 9,000 to 10,000 accounts, from American law enforcement agencies. Facebook said it got 9,000 to 10,000 requests for information about its users, covering 18,000 to 19,000 user accounts, in the last six months of 2012.

How many of those requests were from investigators seeking to sniff out the next terrorist?

The companies said they were not allowed to say, although they noted that the requests were commonly related to things like local police investigations and searches for missing children. That continuing restriction prompted both Google and Twitter to say they would not publish similar data until they could separate national security requests from the rest.