MADRID (Reuters) – Grifols said on Tuesday that Canadian investment fund Brookfield’s potential 6.45 billion euro ($6.8 billion) offer significantly undervalued the Spanish drugmaker’s prospects and long-term potential.

Earlier on Tuesday, Brookfield said it was considering a public offer for Grifols at 10.50 euros per A share and 7.62 euros per B share, implying a company valuation of 6.45 billion euros.

The proposal is non-binding, Brookfield said in a filing to the Spanish stock market regulator.

The Canadian private equity firm said in July it was interested in making a takeover bid jointly with the Grifols family with the ultimate goal of taking the company private.

Grifols said its board would meet later on Tuesday to consider the potential offer, but that, given the valuation, it would not be in a position to recommend that shareholders accept it.

Grifols shares were down 6% at 1310 GMT, one of the biggest falls on Spain’s blue-chip IBEX 35 index.

The company has lost about 30% of its market value since January, when short-seller fund Gotham City Research accused Grifols of overstating earnings and understating debt, which Grifols denied.

On Tuesday, an investigating magistrate at Spain’s High Court opened a probe into Gotham’s actions saying it had found enough evidence to merit an investigation into the possible violation of market and consumer protection laws.

($1 = 0.9472 euros)

(Reporting by Inti Landauro and Javi West Larrañaga. Editing by Jason Neely and Mark Potter)