Well. This 1998 CNN piece, citing “the latest information from U.S. intelligence sources.,” reports that

Pakistani workers at a test site near the Iranian border have put a nuclear device in a shaft and encased it in concrete. The process, known as “stemming,” would make it difficult to retrieve the device without detonating it.

I like the reaction from then-Foreign Minster Gohar Ayub Khan:

“All intelligence offices of any worth will cover themselves by saying ‘probably,’ ‘possibly,’ ‘if,’ ‘maybe,’ ‘perhaps,'” Khan said. “They have no information as such. What they’re trying to do is make an intelligent guess.”

However, Khan said “nothing whatsoever” was keeping Pakistan from proceeding with a test, and that it was not a case of if Pakistan would conduct a test but when.

Asked when a test might occur, Khan responded, “You want me to be hung? These are not the sort of things one gives on television.”