Solanogen-based lifeforms tried to form a spatial rupture between their tertiary subspace manifold and the regular universe in 2369. They were attracted by a modified sensor array created by Geordi La Forge aboard the USS Enterprise-D and subsequently tried to open the rupture in the ship's cargo bay 4.
The aliens used spatially-inverted tetryon particles to establish the gateway between the universes. It was attempted to close or restrict the rupture from growing by establishing a subspace containment field, but the field was incapable in stopping the rift from growing. Even beaming the affected parts of the bulkhead into space was not an option, as the rupture was emanating severe nucleonic interferences which made obtaining a positive transporter lock impossible.
The rupture was finally closed by bombarding it with a coherent graviton pulse, which neutralized the tetryon emissions. Shortly before the rift was completely closed however, the aliens were able to send what seemed like a probe through the opening. (TNG: "Schisms")