The war of the ride-hailing apps is on. Lyft, Uber's biggest competitor, is expecting to raise $1 billion in additional funding, according to Reuters. The Delaware state filing did not elaborate on who was investing or how much the company had already raised.

Financial filings experts estimated that the company was valued between $3.9 billion and $4.5 billion, according to the Boston Globe. Back in March, Lyft was officially valued at $2.5 billion. This announcement comes weeks after Uber reported an additional $2.1 billion in funding, according to Forbes.

With the increased funding on the horizon, Lyft has become one of the top 25 largest private companies, according to Forbes. Uber is still ahead, however, nearly 12 times larger than the startup.

Lyft's stocks are up in light of the announcement, the stocks now at $26.79, according to the Boston Globe. The stock was previously $19.44.

Lyft has been expanding in other areas too. Earlier this month, partnerships were formed with other ride services Ola and GrabTaxi. These partnerships will help Lyft grow overseas, according to Reuters.

In the first half of 2015, Lyft was on a decline, losing $127 million, according to the Boston Globe. This new round of funding aims to put Lyft back on the market and heighten its competition with Uber.