Bitcoin is back baby! Or so it would seem from the spike heard round the world yesterday. Bitcoin jumped 20 percent in one hour-long window early Tuesday morning, breaching the $5,000 barrier for the first time in months. By Tuesday afternoon, the price had fallen slightly to $4,800, but was still up by more than 15 percent, the largest one day increase in price since April of 2018.

What’s happening? There has been a wide array of explanations for bitcoin’s surge, with people looking for single defining factors behind the move, including mysterious buyers, algorithmic trading, and even an April Fools’ day article that went up a day before the spike.

Here’s what we know:

An algorithmically managed order that was worth about $100 million occurred across exchanges Coinbase and Kraken and Luxembourg’s Bitstamp, according to Oliver von Landsberg-Sadie, chief executive of crypto-finance firm BCB Group. The purchases were synchronized to the hour, and were each for around 7,000 bitcoin. Whoever coordinated these purchases is not yet clear, nor is the cause of them.

There has also been a surge in bitcoin algorithmic trading more generally, with small crypto-oriented hedge funds beginning to rely more on such practices. In light of this, one possible trigger discussed for the spike was that traders had a stop-loss order close to the $4,200 mark, or an order to sell a security when it reaches a certain price, thus limiting an investor’s loss on a position in a security, though it can also cover a short position.

There was also the fleeting (or at least it should have been fleeting) thought that this climb may have been due to a fake report on April Fools’ day, which claimed the Securities and Exchange Commission had approved bitcoin exchange-traded funds (it hasn’t). This is certainly the unlikeliest of theories, as even minimal research would show this to be false.

Some crypto analysts have touted underlying factors for bitcoin rise and have signaled the spike for some time. These include areas such as shifts in moving averages, which are price-based, and the upcoming halving of mining rewards in May of 2020. Before a previous halving in 2016, bitcoin gained momentum for about a full year beforehand.

Again though, what is perhaps most likely is that a combination of all of these factors, including others that haven’t been considered, contributed to the spike. Either way, the crypto community celebrated the first signs of a thaw in the long crypto winter. Spring may well be on the way.