Bitcoin fell below $9,000 Tuesday, the first trading day of May.

The cryptocurrency traded 3.9 percent lower around $8,880 as of 8:49 a.m. ET, according to CoinDesk's bitcoin price index. The decline followed a gain of about 33.5 percent for April.

There was no immediately apparent reason for bitcoin's drop, which began overnight. Bitcoin has struggled to claw back to $10,000 in the last several weeks and remains roughly 36 percent lower for the year.

Bitcoin over the last 12 hours

Source: CoinDesk

Japanese yen accounted for about 41 percent of bitcoin trading volume, according to CryptoCompare. U.S. dollar-bitcoin trading made up about 25 percent, and tether — which is pegged to the greenback — accounted for about 20 percent of trading volume.