Interest in millimeter wave (mmWave) spectrum holder Straight Path Communications continues to soar as the firm said an unnamed suitor has now raised an offer to acquire the company to approximately $3.1 billion.

Straight Path, which earlier this year agreed to a multi-million dollar settlement with the FCC over false license buildout claims, said the unnamed bidder has increased its previous offer for full control of the company from $135.96 per share to $184 per share. Reports suggest the mystery bidder is Verizon.

The increased bid is said to be an all-stock offer and was produced without a known counter offer from any other organization. It has caused a run on Straight Path’s stock, which surged more than 30 percent in early Monday trading to more than $212 per share. Straight Path’s stock was trading at around $32 per share prior to the FCC settlement in early January.

Following the FCC settlement, Straight Path secured $17.5 million in funding from a group of investors led by Clutterbuck Capital Management. The loan was in the form of a senior secured option, with the lenders receiving about 252,000 warrants with a strike price at $34.70.

Analysts noted the new bids have “kneecapped” AT&T’s attempt to secure the Straight Path spectrum licenses, though the carrier does have three days to respond.

“The 28 GHz and 39 GHz spectrum bands are obviously an important part of 5G plans, so there is indeed a lot of interest in these assets,” said Bill Ho, analyst at 556 Ventures. “Though a conspiracy theory view on the action would also suggest Verizon is simply jacking up the price to make sure AT&T does not walk away from the deal without paying a hefty price.”

AT&T’s initial offer, which was made last month, was for $95.63 per share and a total value of $1.6 billion. The offer, which continues to have the “favor” of Straight Path’s board, includes a $38 million termination fee to be paid to AT&T should the deal fall apart. Straight Path said it intends to continue in “good faith” negotiations with AT&T, but that the new bidder has agreed to pay the termination fee.

The latest offer continues to increase the value of Straight Path’s bevy of spectrum licenses, which includes 868 licenses in the 28 GHz and 39 GHz bands that are seen as important to the deployment of 5G network technologies. Despite concerns over the ability to monetize mmWave spectrum licenses in support of commercial services, the industry is moving aggressively to include bands above 15 GHz for 5G services due to the quantity of capacity available compared with traditional cellular license bands.

The 28 GHz and 39 GHz spectrum bands are central to the FCC’s “Spectrum Frontiers” proposal launched last year in an effort to free up gigahertz of mmWave spectrum resources in support of 5G services. A number of domestic operators have already begun to trial next-generation services using mmWave spectrum, including Verizon, AT&T, T-Mobile US, Sprint, U.S. Cellular, and C Spire.