On April 23, according to mempool data, an empty block (a block containing only one transaction, the Coinbase transaction) was mined at Bitcoin height 840421, with a time interval of only 27 seconds from the previous block height.

Miners package empty blocks for economic reasons, as it is the most sensible choice for them. In order to fully utilize this time for mining and avoid conflicts with transactions packed in the parent block, miners cannot fill the block with transactions, which means they can only attempt to mine empty blocks.